1. Field of the Invention
The present invention relates generally to radar systems. More particularly, the present invention relates to a decoder circuit which receives Non-Return-To-Zero-Level (NRZL) Data and decodes the Non-Return-To-Zero-Level Data to provide radar video data which is then supplied to a radar video display screen for viewing by the user of the radar display screen.
2. Description of the Prior Art
The military often locates a ground based radar at a site which is remote from the receiving station where the data from the radar is processed and then observed on radar video display screen. The distance between the ground based radar and the receiving station may be several miles which often requires that the radar data be transmitted over public lands via, for example, fiber optic cables. Since data from the ground based radar generally includes classified information there is a need to protect the data during the transmission thereof over the fiber optic cables linking the ground based radar to the receiving station. This requires that the radar data, which is generally in an analog format, be digitized for compatibility with digital formatted encryption units, such as the KG194 encryption unit, currently being utilized by the United States Armed Forces.
The encrypted data is next transmitted via the fiber optic cable to the receiving station where it is un-encrypted by a second encryption unit and then provided in a digital format for processing and then display on a radar video display screen. However, the digitized radar data must be supplied in an analog format which is compatible with the radar video display screen.
It is therefore an object of the present invention to provide radar video data which is compatible with a radar video display screen allowing the user of the radar video display screen to observe data provided by a remote site radar.
It is another object of the present invention to generate the radar trigger pulse which initiates a new sweep of the radar video display screen.
It is yet another object of the present invention to provide range marker signals to the radar video display screen so that the radar video display screen will display range markers thereon.
Other objects, advantages and novel features of the present invention will become apparent to those skilled in the art after reviewing the following detailed description of the preferred embodiment in conjunction with all of the figures of the drawings.